1. Field of the Invention
The present invention relates to the use of selected hydrazidothioate compounds as load-carrying additives for functional fluids such as lubricants and hydraulic fluids.
2. Description of the Prior Art
The employment of chemical additives in lubricants, hydraulic oils and similar functional fluids to improve the overall load-carrying characteristics of the fluid is well known. Probably, the most commonly employed load-carrying additives are the zinc dialkyl and diaryl dithiophosphates. However, for many applications, it is necessary to employ ashless formulations (i.e. formulations that leave substantially no ash residue upon evaporation or combustion). In such instances, the above-mentioned zinc-containing compounds are not satisfactory.
Many load-carrying additives have, alternatively, been found which have this desired ashless characteristic. However, there is still a need in the art to find more suitable ashless additives. To meet this need is a primary object of the present invention.
The hydrazidothioates used in the present invention have been described in the prior art. See articles by Autenrieth and Meyer, Ber. 58, 848 (1925) and Klement and Knollmueller, Chem. Ber. 93, 1088 (1960). However, neither of these prior art references teach or suggest the present inventive use.